An ink jet printer is an example of a printing apparatus that ejects droplets of ink onto a recording medium, such as a sheet of paper, for printing an image on the recording medium. The ink jet printer includes a print engine having one or more ink jet print heads provided with an ink cartridge that accommodates the ink. In operation of the print engine, the ink is supplied from the ink cartridge to each ink jet print head having ejection nozzles, so that a printing operation is performed by ejection of the ink droplets from selected ejection nozzles.
Often it may be necessary to change the ink or other fluids within a print engine during normal cleaning and maintenance. Alternatively, a printer user may wish to replace an ink color, or replace a color with a different or incompatible type of ink (e.g., magnetic ink character recognition (MICR)), cleaning fluid, or remove trapped air from ink lines within the print engine. However, changing inks and fluids, or removing air from a print engine may be a costly and time consuming task.
For instance, an ink change involves discarding relatively large volumes of costly ink. Moreover, removing such large volumes may result in damage to the print head from which the ink is being used because the ink is typically pulled through the print head by a maintenance station. Further, if a print head is supplied multiple colors of inks it can become difficult to remove one color ink without having to remove the other(s), especially if the different inks consist of different viscosities. Thus, all colors supplied by the print head must be removed during ink removal, resulting in the wasting of the ink that did not need to be removed.
Therefore, a mechanism to improve ink or other fluid removal from a printing system is desired.